b. Usage Dosage. Oral administration is preferred whenever possible.
(1) Prophylaxis of malaria: 500-mg (300-mg base) once weekly, beginning
2 weeks before exposure and continuing for 8 weeks after last exposure in endemic
(2) Oral administration for treatment of malaria: One gram (2 tablets) to
start, followed by one tablet (0.5 -gram) in 6 hours. One tablet is then given daily for the
next two days. Total dosage is four doses over a 3-day period for a total of 2.5-grams
of chloroquine phosphate (1.5-grams of chloroquine base).
(3) Parenteral administration in critically ill malaria clients: One 5-ml ampule
equivalent to 200--mg of base is given intramuscularly. This may be repeated in 6
hours, but total parenteral dosage in first 24 hours should not exceed 4 ampules or 800-
mg of chloroquine base.
(4) For blackwater fever in areas where drug resistance has not been
encountered: 200-mg base diluted with 40--ml of normal saline given slowly
c. Adverse Effects.
(1) Mild transient headaches, pruritis, anorexia, blurring of the vision,
vertigo, diarrhea, malaise, and urticaria have been infrequently reported.
(2) Signs of acute chloroquine intoxication include myocardial depression,
disturbances in cardiac conduction, arrhythmias, hypotension, CNS stimulation with
convulsion, and eventual paralysis of vital brain centers.
Cautions and Warnings.
(1) Chloroquine is extremely toxic for young children. The toxic dose for
children is 20 mg/kg and the lethal dose is 100-mg/kg.
(2) Prolonged use of large doses of chloroquine has commonly produced
retinal changes or visual impairment after several months or years of treatment.
(3) Chloroquine accumulates in the liver and should be used with caution in
clients with liver disease.
It is contraindicated in clients with psoriasis.
Avoid its use in pregnancy unless there is an overwhelming need for it.
Chloroquine may color urine rusty yellow or brown.